The examples listed are not rational. They are examples of 'altruism' for the sake of a 'warm feeling' and signalling. Writing a letter, ringing a politician or giving blood are not actions that maximise your altruistic preferences!

You have responded to this 'Potential Objection' with the "better than nothing" argument but even with that in mind this is not about being rational. It is just a bunch of do-gooders exhorting each other to be more sacrificial. When we used to do this at church we would say it was about God... and premising on some of the accepted beliefs that may have been rational. But it definitely isn't here.

I make a call for a different response. I encourage people to resist the influence, suppress the irrational urge take actions that are neither optimal signals nor an optimal instrument for satisfying their altruistic values.

This isn't a religious community and 'rational' is not or should not be just the local jargon for 'anything asserted to be morally good'.

If my preferences were such that I valued eating babies then it would be rational for me to eat babies. Rational is not nice, good, altruistic or self sacrificial. It just is.